U.S. Pat. No. 3,915,237 to E. J. Rozniecki illustrates a fire extinguisher bottle containing liquid fire suppressant and installed in a military vehicle for suppression of near explosive fires caused by passage of enemy projectiles into the vehicle fuel tank. Similar bottles have been used to suppress slow growth fires resulting from debris accumulation or oil accumulations in vehicle crew compartments or engine compartments. Such bottles commonly utilize quick-opening discharge valves of the type shown in U.S. Pat. No. 3,491,783 to O. L. Linsalato. Commonly, an inert pressurized gas, such as nitrogen at 700 p.s.i., is charged into each bottle to provide the driving force for expelling the liquid from the bottle when an electrical signal is applied to the valve actuator.
The present invention is directed to a method of recharging such bottles, using one or more transfer cylinders to accurately meter into each bottle precise quantities of liquid fire suppressant and pressurizing gas on a weight basis. My invention is particularly suited for recharging fire extinguisher bottles in military vehicles without first having to remove the bottles from the vehicles. One advantage of my invention is that the rather heavy bottles do not have to be lifted through the vehicle turret and out the hatch, thus avoiding a potential skin burn hazard due to accidental discharge of liquid fire suppressant should the valve on the bottle strike an obstruction in the vehicle. Also, because there is no need to remove bottles from the vehicles there is a lesser inventory of charged bottles stored at the depot and lesser potential slow leakage associated with stored bottles; bottle maintenance costs should be somewhat less using my invention when compared to present practice. Another advantage of my invention is the elimination of charging inaccuracies that can occur when the liquid suppressant and pressurized gas are introduced on a pressure basis. Such inaccuracies are due to the effect of temperature variations and the characteristic of the pressurizing gas to dissolve slowly in the liquid fire suppressant over a prolonged time period so as to effectively lower the pressure from its initial charge-in value.